Method of printing on glassware and earthenware such as tumblers and similar

ABSTRACT

An elastic layer made of sparingly cross-linked polymeric hydroxyalkyl methacylates is used for printing ethereal oil containing printing liquids on glassware and earthenware articles.

United States Patent 1111 3,632,381

[72] Inventors Richard Chromecek [50] Field of Search 1 17/94, 43, Praha; 38, 124 R; 204/331,28 Leopold Meinhold, Hermanova Hut; Jaroslava Otoupalova; Vlastimil Referellm Ciled Kruntorad, both of Prague, all of UNITED STATES PATENTS Czechoslovakia 3,497,577 2/1970 Wichterle 264/162 1 1 pp 764,659 3,256,372 6/1966 14611111161111... 264/38 1 Flled 1 1968 3,171,869 3/1965 Weinberg 264/331 Patented Jan-411972 3,047,417 7/1962 Melrose 117/43 1 Assignee Ceskoslovenska akadefnie ved 2,976,576 3/1961 Wichterle 61111. 264/49 Prag'1e1CZehSlvak1a 2,733,460 4 1960 RiChlel'Clal. 264 28 Prlomy Oct-511967 2,927,346 3/1960 11111 264 331 1 Czechoslovak 2,626,222 1/1953 Spencer 117 94 31 7034-67 Pnmary ExammerAlfred L. Leavm Asxismnt ExaminerM. F. Esposito 54 METHOD OF PRINTING 0N GLASSWARE AND Attorney-Richard Low EARTHENWARE SUCH AS TUMBLERS AND SIMILAR 1 claim, No Drawings ABSTRdCT: An elast1c layer made of s par1ngly cross-l mk ed polymerlc hydroxyalkyl methacylates 15 used for pnnung [52] US. Cl 117/38, ethereal oil containing priming liquids on glassware d 117 43, 117/94, 117/124 R, 264 28, 264/331 earthenware articles. [51] 1111.0 ..C03c 17/00,

METHOD OF PRINTING N GLASSWARE AND EARTHENWARE SUCH AS TUMBLERS AND SIMILAR Object of the invention is the use of elastic layers made of polymeric sparingly cross-linked hydroxyalkyl methacrylates, manufactured by copolymerizing hydroxyalkyl monomethacrylates with 0.12.0 weight percent of cross-linking agent, namely dimethacrylate or trimethacrylate of a dihydric or trihydric alcohol, in presence of a hydroxylated hydrophilic diluting agent selected from the group consisting of water, ethylene glycol, polyethylene glycols methyl and ethyl monoethers of said glycols and glycerol, for printing metallic compounds, metals, dyes, silicone coatings and similar onto rims of tumblers, dishes and other glass and crockery articles. In order to increase their mechanic strength, the elastic layers, usually forming the outer layer of a printing roller, are advantageously reinforced by textile material or plastic rubber foam or by active fillers, preferably finely divided silicon dioxide, or by both of them. The final shaping of the swollen elastic layers is carried out by means of machine tools at temperatures between 0 and 190 C., preferably between and 80 C.

Neither printing rollers as such, nor the whole printing device are object of the present invention. The object of the invention is the outer elastic layer of known printing rollers in the known device for printing rims of glass tumblers, dishes and other glass and crockery articles, and the method of preparing said elastic layer. Elastic layers are used in usual way by leading the ware to be printed on a transporter under the printing roller, the rim of the tumblers or similar being slightly pressed against the soft elastic layer onto which the printing liquid (solution or suspension) is applied by means of an inking roller. Thereby the required amount of the printing liquid is applied on, forming a rim of regular width, which is then fixed e.g., by burning, if needed.

Elastic layer on printing rollers of the above mentioned kind has to withstand to different organic solvents such as benzene, nitrobenzene, ethyl acetate, dekahydronaphthalene as well as to various ethereal oils such as eucalyptus-, rosemary-, turpentine and clove oil and their mixtures.

Until now, the elastic layers of the above described kind have been manufactured from water swollen gelatine, which resists to the above-mentioned solvents and ethereal oils. Water swollen gelatine has, however, some severe shortcomings such as cracking upon drying on the air. The rollers must be thus kept in humid atmosphere, without being, however, in direct contact with water in which gelatine dissolves. The service life of gelatine layers is short-about -50 operation hours. Crosslinking with formaldehyde or similar removes the solubility, but the gelatine becomes thereby too hard, its elasticity and softness, necessary for adequate printing, being unsatisfactory.

Said shortcomings are avoided if, according to the invention, water swollen gelatine is replaced by a swollen hydrogel consisting of a copolymer of a hydroxyalkyl methacrylate with 0.1 to 2.0 percent of a cross-linking agent, preferably a glycol dimethacrylate or glycerol dior trimethacrylate or their mixtures. Said dimethacrylates are very convenient, being usually present in hydroxyalkyl monomethacrylates as an admixture which cannot be easily removed. Said hydrogels are known per se e.g., from the US. Pat. Nos. 2,976,576 and 3,220,960, where their use for making soft contact lenses and different surgical and chirurgical articles has been disclosed. It is surprising that genuine gelatine, displaying unlimited swelling capacity in water, can be successfully replaced by more tough sparingly cross-linked glycol methacrylate hydrogels with limited swelling capacity. Furthermore, it could not be presumed that such chemically simple hydrophilic polymers would possess good wettability with water-immiscible organic solvents and ethereal oils, the wettability depending upon some chemical sidegroups which are of various kinds in the gelatine whilst hydroxyalkyl methacrylates possess only two of them, namely the hydrophilizing primary alcoholic and the hydrophobizing methylic group.

The limited swelling capacity, accompanied with absolute insolubility in water, makes possible keeping elastic layers directly in water or in polyhydric alcohol such as ethylene glycol or glycerol. The use of polyhydric alcohols for diluting the polymerizing mixture and for maintenance of elastic layers is much more advantageous than the use of water, the operation cycle as well as the total service life being substantially extended.

Elastic layers according to the invention can be easily manufactured by polymerization-casting of diluted monomeric mixtures in a mold with annular cross section consisting of two concentric cylinders with different diameter, the outer cylinder having a bottom and the inner cylinder forming the central pin. Advantageously, said inner cylinder is formed by the cylinder of the printing roller so that the elastic layer is polymerized directly onto the roller with the result that it is not necessary to put or slip the elastic layer onto said roller and that the bond is very firm. The elastic layer can be reinforced by a textile or plastic foam insert put onto the inner cylinder of the mold prior to pouring the monomeric mixture into the mold. The cast, still liquid monomer mixture can be degasified by applying vacuum, in order to prevent gas bubbles. This is particularly important when using textile or plastic foam reinforcing inserts.

Hydroxyalkylmonomethacylates, used as main monomeric component, are usually glycol monomethacrylates such as ethylene glycol monomethacrylate, diethylene glycol monomethacrylate and similar. Glycerol monomethacrylate can be used instead. Monomethacrylates of other polyols such as pentaerythritol or mannitol can be also used, although their preparation and purification from superfluous diand trimethacrylates causes considerable difficulties. The amount of cross-linking diand trimethacrylates must not exceed 2.0 weight percent, in order to obtain appropriate softness and elasticity.

The polymerization can be initiated by usual free radical polymerization initiators such as organic peroxides, hydroperoxides, persulfates and their mixtures with reducing agents, forming, usually in presence of iron or copper ions, effective redox systems. It is, however, possible to set the polymerization working by means of UV- or gamma rays in the known manner. If desired, the polymerization is aided by heating.

Hydroxylated diluting agents are added to the monomers in order to obtain the elastic layer in proper size and condition. Elastic properties can be changed in broad limits by the amount of the diluting agent added. Using e.g., water as diluting agent, one obtains with less than 40 percent tough, transparent hydrogels. With 40 to 60 percent of water, the obtained hydrogels are softer and more or less opaque due to very small voids. With more than 60 percent of water the resulting hydrogels are soft and porous. The optimum value for water lies within 40 and 60 percent. If, however, dihydric or polyhydric alcohols such as ethylene glycol, diethylene glycol or glycerol are used as diluting agents, the useful range lies within far broader limits, for instance between 20 and percent in the case of glycerol, or 10 and 80 percent in the case of ethylene glycol, according to the desired elasticity and softness. Other hydroxylic compounds such as saturated monoethers and monoesters of glycols, as well as glycerol diesters can be also used as diluting agents.

Changing thus the sort and the amount of the diluting agents, one can obtain elastic layers with various porosity and suction capacity for the printing liquid. It is also possible to combine two or more layers of different porosity and softness.

Naturally, the diluting agents are to be chosen so that they do not interfere with the printing process, particularly by forming co-solvent mixtures by which the elastic layer would be exceedingly swelled, Suitable diluting agents are immiscible with printing liquids. Most appropriate are such which cannot be easily squeezed out from the layer, e.g., glycols. The same agents are then used also for the maintenance of the elastic layers. The maintenance consists in that the elastic layer, washed from the remnants of the printing liquid, is either stored in the liquid used as diluting agent or the latter is simply applied onto the surface by dipping, brushing or similar.

The mechanical properties and the abrasion resistance of the elastic layer can be improved by adding active fillers to the monomeric mixture. Very suitable filler is finely divided silicon dioxide added preferably in an amount of 5 till to 40 percent, computed on the sum of monomers and diluting agents.

in order to avoid sedimentation of the filler prior to the advanced polymerization and to maintain homogenity of the layer, it is advantageous to increase the viscosity of the monomeric mixture by adding 1 to 80 percent of soluble hydroxyalkyl methacrylate polymer or copolymer with the corresponding dimethacrylate. Soluble polymeric hydroxyalkylmonomethacylate (glycol monomethacrylate) possesses the same chemical composition as the polymer of the elastic layer except that it is not cross-linked. Soluble copolymers of this kind can be easily prepared by carrying out the copolymerization in presence of a good solvent, having the interaction parameter x with respect to the copolymer lower than 0.5 and having simultaneously a considerable swelling capacity for the cross-linked copolymer of the same kind, gained by carrying out the copolymerization in presence of a bad solvent (parameter x higher than 0.5), e.g., water. Good solvents are e.g., methanol, formamide, dimethyl formamide, ethylene glycol monomethyl ether and similar. The process is described in detail e.g., in the French Pat. No. 1,523,779.

As reinforcing inserts various textile materials such as fabrics, webbings or knitted fabrics from natural and man made fibers can be used, such as cotton, wool, flax, viscose rayon, acetate rayon, polyamide, polyester, polyacrylonitrile, and other fibers. Among, plastic foams e.g., polyurethane soft foams, foamed rubber or viscose sponge can be used, if desired in a combination with fibrous materials.

For exact printing, to obtain fine and uniform rims on the tumblers or similar, the surface of the elastic layer must be regular, even and glossy. This can be accomplished conveniently by working or shaping by means of machine tools such as a lathe, in frozen condition, i.e. at 0 to l90 C., preferably between and 80 C.

This is accomplished by immersing the swollen elastic layer on the roller into a cooling bath prior to machining. The cooling bath must not contain solvents with substantially higher swelling capacity for the polymer than that of the diluting agent. During the working on the machine tool the elastic layer. can be cooled by a stream of the same cooling liquid. The swollen elastic layer can be readily milled, machine-cut, filed, ground, lathe-tumed, bored etc.

Damaged elastic layer can be repaired by a combination of machining and polymerizing. The outer layer of the swollen and frozen polymer is grooved on a lathe, a new reinforcement insert is applied, if desired, and a new monomeric mixture is polymerized in the mold onto the surface.

The elastic layer according to the invention is suitable not only for gilding or coloring rims of glass and ear'thware tumblers and similar, but also e.g., for applying other materials such as silicone resins onto the bottle necks, or solutions of mineral salts onto various earthware and crockery.

The invention is illustrated by following, nonlimiting examples.

EXAMPLE I A flat elastic printing layer was manufactured using a flat glass mold l l25 30 mm., which was filled up with a mixture of 270 ml. of ethylene glycol monomethacrylate (containing 0.2 percent dimethacrylate), wherein 1.8 g. of dibenzoyl peroxide has been previously dissolved, with a solution of 1.2 ml. of dimethylamino ethyl acetate in 180 ml. of water. The mold was then immersed into a cooling bath and the cooling adjusted so that the temperature of the polymerizing mixture was 20 to 25 C. At the very beginning, just after the ingredients have been mixed, the mixture was degasified by applying vacuum. The surface of the liquid in the mold was kept under inert gas (e.g., nitrogen or carbon dioxide). The polymerization lasted 8 to If) hours. Then the soft elastic sheet was removed from the mold and washed for 24 hours-in water. The washed, fully swollen sheet was cooled down to a temperature from 40 to 50 C. and milled to the final size of l20 l2 0 20 mm. After having been heated again to ambient temperature, the sheet was wetted with usual gilding solution and glass tumblers were pressed with their rims onto it. The gilding was developed and fixed by burning in usual way.

EXAMPLE 2 A steel, tin-coated mold consisted of a cylindrical vessel, diameter 220 mm., in which another cylinder, diameter 150 mm., was concentrically fixed. The space between the two cylinders was filled with a mixture of two solutions. One solution consisted of 9 g. dibenzoyl peroxide in L950 ml. of raw ethylene glycol monomethacrylate (85.6 percent), containing 0.22 percent of ethylene glycol dimethacrylate, the rest to percent being ethylene glycol. The other solution consisted of 6 ml. of dimethylamino ethyl acetate in 1,050 ml. of water. The mold was then closed, the air over the surface was replaced by carbon dioxide and the polymerization carried out at 20 to 25 C. After having been removed from the mold, the elastic hollow cylinder thus obtained was washed for 24 hours in water, slipped onto the steel printing roller and milled to the outer diameter of 210 mm. and the length of 1 l0 mm. Prior to the milling, the roller was immersed into a mixture of dry ice with xylene and cooled therein to from 40 to 70 C. The coated roller was used in conventional machine for gilding rims of glass tumblers, which were moved on a conveyor. The printing roller was driven by an electric motor with gears, and the printing liquid was applied onto it by a small steel roller. The tumblers on the conveyor were pressed slightly into the elastic layer and led into an electric baking oven where the gilded rim was fixed at temperatures between 480 and 560 C.

The roller was kept in operation for 24 hours in order to avoid drying of the elastic layer. Then it was washed with benzene or decaline and immersed into water for 8-16 hours. The drying is caused by organic solvents contained in the printing liquid, and if lasting longer, it might cause cracking of the elastic layer. The total service life was 100-150 hours.

EXAMPLE 3 The elastic layer was manufactured in the way disclosed in example 2 except that a cylindrical reinforcement insert of a loose 15 mm. thick nylon knitted fabric was previously slipped onto the inner cylinder of the mold. The reinforced elastic layer had higher strength than that according to example 2. The gilding was carried out in the same manner as in example EXAMPLE 4 The process according to example 3 was repeated, only the nylon insert was replaced by a humid viscose sponge from which water has been squeezed out. The mechanical properties were improved, compared with the elastic layer according to example 2.

Similar results were obtained if the polymer was reinforced by rubber foam, soft polyurethane foam, or by a loose roll of polyethylene terephtalate, flax, cotton or wool fabric of the same thickness of about 15 mm.

EXAMPLE 5 The same mold as used in example 2 was filled up with following mixture: 9 g. of dibenzoyl peroxide were dissolved in 1,950 ml. of the raw ethylene glycol monomethacrylate of the quality stated in example 2. The solution was mixed with a slurry of 400 g. of finely divided silica (particle size 0.1-0.5

microns) rubbed with 1,000 ml. of water. Finally, 6 ml. of dimethylamino ethyl acetate were rapidly stirred into the homogenized mixture and the whole was poured into the mold. The mixture was polymerized at 25 C. for 8 hours. The elastic ring was treated like in example 2 and used for gilding of tumbler rims. lt possessed substantially higher strength than the nonfilled polymer.

EXAMPLE 6 The process according to example 5 was repeated except that the monomeric ethylene glycol methacrylate was previously mixed with percent of its weight of a soluble ethylene glycol methacrylatedimethacrylate copolymer, obtained by polymerizing the same raw monomer in 80 percent of methanol at 66 C. for 5 hours with 0.5 percent of dibenzoyl peroxide as polymerization catalyst. The increasing of viscosity of the mixture resulted in improved homogenity, the sedimentation of the filler being prevented.

EXAMPLE 7 The process according to example 2 was repeated, replacing water as diluting agent subsequently by ethylene glycol, diethylene glycol, triethylene glycol, mixtures of polyethylene glycols with average molecular weight of 300, 600, 1,500 and 3,000, and by glycerol with various water content (from 10 to 90 percent). In all cases good elastic rings with increased strength were obtained. In the first case-with ethylene glycol as diluting agent-could the printing roller be operated for 8 hours continuously. Thereafter the elastic layer was washed with decaline, wiped off and then ethylene glycol was applied onto it. The use of glycol for diluting the polymerization mixture and maintenance has the advantage of increasing the operation cycle and the service life, the latter amounting to more than 300 operating hours. Further extension of the service life can be achieved by adding active filler according to example 5, stirred in ethylene glycol instead of water.

EXAMPLE 8 In the process according to example 2 ethylene glycol monomethacrylate was replaced by diethylene glycol monomethacrylate, containing 0.4 percent of the respective diester. The elastic layer thus obtained was more swellable than that according to example 2, but still satisfactory as to the strength and abrasion resistance. Similar results were obtained if triethylene glycol monomethacrylate or glycerol monomethacrylate with less than 2 percent of the cross-linking dior trimethacrylates was used.

EXAMPLE 9 The elastic layer according to examples 2 and 3 (with nylon reinforcement) was manufactured in similar mold, where the inner cylinder was replaced by the printing roller. Thereby a very good bond between the steel roller and the soft elastic layer was obtained.

The same process was repeated adding active silica filler according to example 6 and ethylene glycol or glycerol as diluting agent in the polymerization process according to example 7. The resulting elastic layer had outstanding strength and abrasion resistance. The operation cycle and the total service life were substantially extended in comparison with example 2.

EXAMPLE 10 The elastic ring obtained by the method described in example 2 was, after having been washed in water, immersed into ethylene glycol. The elastic layer thus obtained had longer operating cycles and service life than that according to example 2, swollen with water only.

It is to be born in mind that the amount of the diluting agent other than water is to be chosen so that insoluble, cross-linked polymer is always obtained. Said amount depends also on various factors, e.g., presence of fillers and the nature of the diluting agent: it can be higher e.g., when using glycerol than when using a glycol. The content of the cross-linking agent and the amount of the polymerization catalyst have also their influence in this respect.

The percentage is generally meant by weight, if not stated otherwise.

What we claim is:

1. In the process of printing on glassware and earthenware hollow articles, by pressing said articles to an elastic layer wetted with printing liquid containing an ethereal oil, the improvement comprising the use of an elastic layer made of sparingly cross-linked polymeric hydroxyalkyl methacrylates, formed by copolymerizing hydroxyalkyl monomethacrylates with 0.1 to 2.0 percent of a cross-linking agent, in the presence of a hydroxylated hydrophilic diluting agent selected from the group consisting of water, ethylene glycol, polyethylene glycols, methyl and ethyl monoethers of said glycols, and glycerol. 

